This application claims priority from Korean Patent Application No. 2003-45411, filed on Jul. 4, 2003, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
This disclosure relates to a temperature sensing circuit, and more particularly, to a temperature sensing circuit in which the temperature in a semiconductor device is sensed.
2. Description of the Related Art
A conventional thermal sensor senses the temperature in a semiconductor device and outputs the sensed result only as a ‘high’ or ‘low’ level.
For example, a thermal sensor designed to sense a predetermined reference temperature outputs a ‘high’ level when a present temperature in a semiconductor device is higher than the predetermined reference temperature, and outputs a ‘low’ level when the present temperature in the semiconductor device is lower than the predetermined reference temperature.
Thus, in order to sense temperature in the semiconductor device accurately, a plurality of thermal sensors would be required. For example, in order to sense a temperature in the semiconductor device where the operating temperature range of the semiconductor device is 100° C. and an accuracy of 1° C. is desired, 99 thermal sensors are needed.
FIG. 1 illustrates an operating principle of a conventional thermal sensor. A conventional thermal sensor uses two currents, CTAT and PTAT. CTAT is generated by applying a forward bias to a P-N junction and has a characteristic that the magnitude of the current decreases as temperature increases. PTAT is generated by applying a forward bias to a P-N junction and has the characteristic that the magnitude of the current increases as temperature increases.
The two currents PTAT and CTAT, having inverse characteristics, are applied to input terminals of a comparator (not shown). For example, the current PTAT is applied to a positive terminal of the comparator (not shown), and the current CTAT is applied to a negative terminal of the comparator (not shown). Then, the output of the comparator (not shown) is observed.
Referring to FIG. 1, when the temperature is below a reference temperature REFT, the current CTAT is larger than the current PTAT, and the comparator (not shown) outputs a low level. When the temperature is higher than REFT, the current PTAT is larger than the current CTAT, and the comparator (not shown) outputs a high level.
The temperature at which the two currents PTAT and CTAT intersect is the reference temperature REFT. The reference temperature REFT may be arbitrarily set by a designer when the designer designs the thermal sensor.
Thus, by observing the output of the comparator (not shown), whether the present temperature in the semiconductor device is higher or lower than the reference temperature REFT can be determined. However, the conventional thermal sensor indicates only whether the present temperature in the semiconductor device is higher or lower than the reference temperature REFT. It cannot sense the temperature in the semiconductor device with any greater accuracy.
Embodiments of the invention address these and other limitations of the prior art.